Heat interchange



March 23, 1954 I w. w. SPOONER HEAT INTERCHANGE 2 Sheets-Sheet 1 Filed Aug. 3, 1950 LL 2 u mm f 17 :f

I nventor,

March 23, 1954 w w SPOONER 2,673,073

HEAT INTERCHANGE Filed Aug. 3, 1950 2 Sheets-Sheet 2 Patented Mar. 23, 1954 2,673,073 HEAT INTERCHANGE William Wycliffe Spooner, Ilkley, England Application August 3, 1950, Serial No. 177,437

Claims priority, application Great Britain August 5, 1949 2 Claims; (01. 257-437) The present invention relates to heat interchange, and can be applied to th heating of any solid and/or liquid and/or gaseous material to be heated by a gaseous heating medium. The invention is especially applicable to the heating of water to increase its temperature or to the raising of steam or superheated steam.

An important feature of the invention consists in heating any solid and/ or liquid and/or gaseous material or materials with a gaseous medium at relatively low temperature (i. e. at a temperature not very much higher than th desired temperature of the material to be heated), by passing the medium around a closed circuit and repeatedly causing it to flow at relatively high velocity over the material to be heated or over the surface or surfaces containing it.

According to another feature of the invention the temperature difference between the heating medium and the desired temperature of the material to be heated is low and of the order of or 50 F. and never in excess of 100 F.

In a conventional boiler for heating water, for example, or for raising steam, the gaseous medium used for heating, i. e, usually products of combustion, impinges upon the surfaces containing the water at relatively high temperature, such for example as 3000 F. and usually leaves the heating system at a fairly high temperature, say 800 F. Thus in such heating installations a good deal of the heat in the heating medium, i. e. the heat remaining in the medium as it leaves the installation, is considered as unavailable, and, moreover, the initial high temperature of the heating medium is always attended by the risk of burning out portions of the installation should it become short of water. By means of the present invention heating media at relatively low temperature can be rendered available for the heating purpose and the risk of burning out the installation through shortage of water can be eliminated.

It is envisaged that, by means of the present invention, water could be heated satisfactorily and quite quickly, or steam could likewise be raised, by using a heating medium whose temperature is only say between 20 and 50 F. higher than the final temperature required of the water or steam.

In a particular installation, taken by way of example, a set of finned heating coils or tubes for heating water or raising steam may be arranged in a closed circuit with a fan, and the heating medium may pass in closed circuit from the fan to the heating coils and from the heating coils back to the fan. The temperatur of the heating of inflow of products ofcombustionfrom the gas lets or oil burners.

Whereas in conventional heating installations the rate of flow of the heating medium through the system is approximately equal to the rate of inflow of the medium into the system, according to the present invention the rate of flow of the heating medium through the system is much greater than the rate of inflow of the heating medium. For example, the rate of flow of the heating medium through the fan, and thus past the heating coils, may be between ten and twenty times the rate of inflow of products of combustion from the gas jets or oil burners, from which it follows that each unit of the heating medium will pass over the heating coils between ten and twenty times.

An important feature of the invention, therefore, consists in a method of and apparatus for heating in which the heating medium is caused to flow in a closed circuit or endless path and in which its volume rate of flow around the circuit is a multiple, and preferably a large multiple which may be as high as or even 400, of the rate of inflow of heating medium into thecircuit.

A further feature of the invention consists in a method of and apparatus for heating as defined immediately above, in which heating medium is passed around the closed circuit at relatively high veolcity.

A still further feature of the invention consists in a method of and apparatus for the heating in which a gaseous heating medium is passed in closed circuit at relatively high velocity and in which the rate of flow of the gaseous medium per minute is greater than and preferably a multiple (say between 10 and 100 or even higher) of the total volume of the medium employed in the system.

From this it will follow that the change in temperature of the heating medium during each pass through the system is low and of the order of 2 F. up to 20 F. whilst the rate of interchange of heat per unit time is great in view of the high velocity of the gaseous medium and the fact that the gaseous medium passes through the system with a high degree of frequency. Thus the invention consists in the giving up or taking up by elements of the gaseous medium of small quantities of heat frequently instead of, as in normal systems, giving up or taking in relatively large quantities of heat relatively infrequently.

In apparatus as described herein, suitable guide and baflle means may be provided for directing the heating medium smoothly where it is required to change direction, and for directing the heating medium relatively uniformly over the heating coils or other surfaces to be heated. Any suitable fan may be employed, such for example as an axial flow fan. v

It will be appreciated that, instead of using gas jets or oil burners, products of combustion from say a diesel engine or waste heat from any other suitable source may be employed, since the temperature of the heating medium may be relatively low.

When gas jets or oil burners or the like are used to maintain the temperature of the heating medium, they should be located at some point in the circuit at which they do not play directly on to the surfaces to be heated, and thus the present invention includes a method of heating in which volumes of a relatively hot heating medium are diluted with larger volumes of a heating medium at lower temperature, and the mixed heating medium, at a temperature which is nearer that of the diluting medium than that of'the relatively hot medium, is caused to flow a number of times and at relatively high velocity over the surface or surfaces to be heated.

The invention is especially applicable in connection with domestic boilers which may be heated by, say, gas or oil fuel, since, by means of the present invention, the risk of burning out is eliminated.

The present invention is also applicable to waste heat boilers using, for example, products of combustion from diesel engines or other sources of waste heat, but it wll be appreciated that the invention has a general application to heat exchangers for many purposes.v

The invention is further described by way of example with reference to the accompanying drawings in which:

Fig. 1 is a diagrammatic sectional view of a heat interehanger which is especially suitable for the heating of water;

Fig. 2 is a fragmentary view of a fan or impeller employed in Fig. 1;

Fig. 3 is a diagrammatic sectional view of a form of construction alternative to Fig. 1.

In the arrangement shown in Fig. 1 an electric motor I drives a fan or impeller 2 located within a casing 3 and arranged adjacent a bank of finned tubes 4 extending between a lower header 4? and an upper header 48 having inlet and outlet connections 49, 50 respectively. The fins of the tubes 4 are indicated at 5. The casing is provided with end covers 5, 1 of annular form. I

As shown in Fig. 2 the impeller 2 has three concentric sets of blades, 8, 9, of which the blades 8 and Ill are similarly inclined Whilst the blades 9 are inclined oppositely to the blades 8 and It as shown diagrammatically by the lines l8, I9, 20 in Fig. 1. Thus the blades 9 will cause a gaseous medium to flow from right to left as viewed in Fig. 1 and as indicated by the arrow 29 whilst the blades 8 and ID will cause the gaseous medium to flow in the opposite direction from left to right as indicated by the arrows 28 and 39.

Because the linear speed of the blades [0 will be greater than that of the blades 9 the pitch of the blades 10 is less than that of the blades 9 and similarly the pitch of the blades 9 is less than that of the blades 8. Moreover the pitch of the indivdual blades decreases outwardly.

Each individual blade is provided with a pair of flanges ll, l2 and the blades are secured in position by riveting or welding of the flanges respectively between hoops l3, l4, l5 and boss l6.

Each end cover 6, l is formed as a dished member with outer and inner annular recesses l'l, 2|, 22, 23 respectively.

Outer and inner guide hoops 24, 25 are arranged between the impeller and the bank of tubes 4 in line with the hoops l4, l5 of the impeller. It will thus be appreciated that with a gaseous heating medium within the casing 3 rotation of the impeller will cause circulation of the gaseous medium through the bank of tubes in two closed circuits one of which will pass through the blades 9, through the tubes -4, around annular chamber 1', back through the tubes, through blades l9 and around the annular chamber ll, whilst the other closed circuit will pass through the blades 9, the tubes 4, around the annular chamber 23, through tubes 4 and blades 8 and around the annular chamber 2|.

The end cover 6 is provided with inlet ducts 26 to permit the inflow of hot gaseous medium which is preferably controlled so as to maintain the temperature of the circulating gaseous medium within the casing at a more or less constant temperature. Thus gas jets as indicated at 2! may be arranged at the mouths of the inlets 26 so that the products of combustion of the gas jets can be drawn into the casing through the inlets 23. The end cover 6 may also have outlets 3| to enable the products of combustion to escape from the casing to compensate for the inflow through the inlets 26.

Thus the present invention provides a relatively inexpensive water heater or steam raiser of light construction which cannot possibly be burnt out since the temperature of the products of combustion circulating in the casing is vastly less than the temperature of the gas jets 21. On the other hand the high speed of flow of the gaseous medium and the re-circulation thereof in closed circuit to afford a volume flow per minute which is large as compared with the rate of inflow of hot products of combustion and which is large as compared with the total volume of the gaseous medium contained in the casing provides a rapid interchange of heat in spite of the relatively low temperature of the circulating gaseous medium.

The alternative construction shown in Fig. 3 is similar to that of Fig. 1 except that the blades 32, 33, 34 of the fan or impeller are all inclined in the same direction so that they all cause flow of the gaseous medium in the same direction as indicated by the arrows 35, 36, 31. Thus the casing 38 is shaped somewhat diiferently as compared with that of Fig. l to cause the gaseous medium to flow in a single closed circuit. Fresh gaseous medium is introduced at inlets 39 which correspond to the inlets 26 of Fig. 1 and the casing 38 is provided with outlets 40 which correheaders being indicated at 43 and 44. and the in- 1ets and outlets of the respective headers being indicated at 45 and 46.

I claim:

1. A heat exchange apparatus comprising a bank of finned tubes, inlet and outlet means to said finned tubes for admission and withdrawal of material to be treated, an axial flow fan located adjacent said finned tubes and comprising at least three concentric sets of blades of which the inner and outer sets are similarly inclined and the intermediate set oppositely inclined so that the intermediate set of blades will cause a flow of gaseous medium around said finned tubes in one direction while the inner and outer sets will cause a flow of gaseous medium around the tubes in the opposite direction, a casing enclosing said tubes and fan including cover members on opposite sides thereof of dished form each including an inner and outer annular recess which adjoin approximately at the mid-diameter of the intermediate set of blades to enable a gaseous medium in the casing to flow in two closed circuits one through the intermediate set of blades around the tubes and back through the outer set of blades, and the other through the intermediate set of blades through the tubes and back through the inner set of blades, said casing having at least one inlet for the inflow of fresh gaseous medium thereto and at least one outlet for the escape of gaseous medium therefrom and the fan being of a capacity sufiicient to cause a volume rate of flow in the closed circuit which is a large multiple, upwards of 40 times and preferably of the order of 100 to 400 times, the rate of inflow of gaseous medium to the casing.

2. A heat exchange apparatus comprising a bank of finned tubes, inlet and outlet means to said finned tubes for admission and withdrawal of material to be treated, a fan located adjacent said finned tubes and comprising at least three concentric sets of blades of which the inner and outer sets are similarly inclined and the intermediate set oppositely inclined so that the intermediate set of blades will cause a flow of gaseous medium around said finned tubes in one direction while the inner and outer sets will cause a flow of gaseous medium around the tubes in the 0D- posite direction, a casing enclosing said tubes and fan including cover members on opposite sides thereof of dished form each includin an inner and outer annular recess which adjoin approximately at the mid-diameter of the intermediate set of blades to enable a gaseous medium in the casing to flow in two closed circuits one through the intermediate set of blades between and around the tubes and back through the outer set of blades, and the other through the intermediate set of blades between and around the tubes and back through the inner set of blades, said casing having at least one inlet for the inflow of fresh gaseous medium thereto and at least one outlet for the escape of gaseous medium therefrom and the fan being of a capacity sufiicient to cause a rate of flow per minute of the gaseous medium in the closed circuit which is greater than and preferably a relatively large multiple of the total quantity of the gaseous medium in the circuit.

WILLIAM WYCLIFFE SPOONER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 432,282 Proctor et a1 -1 July 15, 1890 1,564,566 Harris Dec. 8, 1925 1,996,927 Lake Apr. 9, 1935 2,158,258 Sucharski May 16, 1939 2,274,033 Booth Feb. 24, 1942 2,275,295 Greenway Mar. 3, 1942 

